Process for controlling ionic liquid catalyst activity by titration

ABSTRACT

A process for determining ionic liquid catalyst deactivation including (a) collecting at least one sample of an ionic liquid catalyst; (b) hydrolyzing the at least one sample to provide at least one hydrolyzed sample; (c) titrating the at least one hydrolyzed sample with a basic reagent to determine a volume of the basic reagent necessary to neutralize a Lewis acid species of the ionic liquid catalyst; and (d) calculating the acid content of the at least one sample from the volume of basic reagent determined in step (c) is described. Processes incorporating such a process for determining ionic liquid catalyst deactivation are also described. These processes are an alkylation process, a process for controlling ionic liquid catalyst activity in a reaction producing by-product conjunct polymers, and a continuous process for maintaining the acid content of an ionic liquid catalyst at a target acid content in a reaction producing by-product conjunct polymers.

This application is a division of prior application Ser. No. 12/437,515,filed Nov. 26, 2008, and published as US20100129921, herein incorporatedin its entirety. The assigned art unit of the prior parent applicationis 1797. This application claims the benefit of provisional ApplicationNo. 61/118,209, filed Nov. 26, 2008, herein incorporated in itsentirety.

FIELD OF ART

The processes described herein relate to determining ionic liquidcatalyst deactivation. More particularly, the processes described hereininvolve determining ionic liquid catalyst deactivation by titrating oneor more samples of the ionic liquid catalyst with a basic reagent.

BACKGROUND

An alkylation process, which is disclosed in U.S. Pat. No. 7,432,408(“the '408 publication”), involves contacting isoparaffins, preferablyisopentane, with olefins, preferably ethylene, in the presence of anionic liquid catalyst to produce gasoline blending components. Thecontents of the '408 patent are incorporated by reference herein in itsentirety.

An ionic liquid catalyst distinguishes this novel alkylation processfrom conventional processes that convert light paraffins and lightolefins to more lucrative products such as the alkylation ofisoparaffins with olefins and the polymerization of olefins. Forexample, two of the more extensively used processes to alkylateisobutane with C₃-C₅ olefins to make gasoline cuts with high octanenumbers use sulfuric acid (H₂SO₄) and hydrofluoric acid (HF) catalysts.

As a result of use, ionic liquid catalysts can become deactivated, i.e.lose activity, and may eventually need to be replaced. Alkylationprocesses utilizing an ionic liquid catalyst can form by-products knownas conjunct polymers. These conjunct polymers generally deactivate theionic liquid catalyst by forming complexes with the ionic liquidcatalyst. Conjunct polymers are highly unsaturated molecules and cancomplex the Lewis acid portion of the ionic liquid catalyst via theirdouble bonds. For example, as aluminum trichloride in aluminumtrichloride-containing ionic liquid catalysts becomes complexed withconjunct polymers, the activity of these ionic liquid catalysts becomesimpaired or at least compromised. Conjunct polymers may also becomechlorinated and through their chloro groups may interact with aluminumtrichloride in aluminum trichloride-containing catalysts and thereforereduce the overall activity of these catalysts or lessen theireffectiveness as catalysts for their intended purpose.

Accordingly, there is a need for a method for determining ionic liquidcatalyst deactivation so that deactivated ionic liquid catalysts can beeffectively and efficiently replaced when appropriate.

SUMMARY

Disclosed herein is a process for determining ionic liquid catalystdeactivation. The process comprises: (a) collecting at least one sampleof an ionic liquid catalyst; (b) hydrolyzing the at least one sample toprovide at least one hydrolyzed sample; (c) titrating the at least onehydrolyzed sample with a basic reagent to determine a volume of thebasic reagent necessary to neutralize a Lewis acid species of the ionicliquid catalyst; and (d) calculating the acid content of the at leastone sample from the volume of basic reagent determined in step (c).

Also disclosed herein are processes utilizing an embodiment of theprocess for determining ionic liquid catalyst deactivation as disclosedherein. They include an alkylation process that determines ionic liquidcatalyst deactivation, a process for controlling ionic liquid catalystactivity in a reaction producing by-product conjunct polymers, and acontinuous process for maintaining the acid content of an ionic liquidcatalyst at a target acid content in a reaction producing by-productconjunct polymers.

In one embodiment, an alkylation process comprises: (a) reactingisoparaffins with olefins in the presence of an ionic liquid catalyst toprovide a hydrocarbon product; (b) collecting samples of the ionicliquid catalyst at regular intervals; (c) hydrolyzing the samples toprovide hydrolyzed samples; (d) titrating the hydrolyzed samples with abasic reagent to determine a volume of the basic reagent necessary toneutralize a Lewis acid species of each sample; (e) calculating the acidcontent of each sample from the volume of basic reagent determined instep (d); and (f) regenerating the ionic liquid catalyst when the acidcontent reaches a predetermined level to provide a regenerated ionicliquid catalyst.

In another embodiment, a process for controlling ionic liquid catalystactivity in a reaction producing by-product conjunct polymers comprises:(a) using an ionic liquid catalyst in a reaction producing by-productconjunct polymers; (b) collecting samples of the ionic liquid catalystat regular intervals; (c) hydrolyzing the samples to provide hydrolyzedsamples; (d) titrating the hydrolyzed samples with a basic reagent todetermine a volume of the basic reagent necessary to neutralize a Lewisacid species of each sample; (e) calculating the acid content of eachsample from the volume of basic reagent determined in step (d); and (f)regenerating the ionic liquid catalyst when the acid content reaches apredetermined level to provide a regenerated ionic liquid catalyst.

In yet another embodiment, a continuous process for maintaining the acidcontent of an ionic liquid catalyst at a target acid content in areaction producing by-product conjunct polymers comprises: (a) using anionic liquid catalyst in a reaction producing by-product conjunctpolymers; (b) collecting samples of the ionic liquid catalyst at regularintervals; (c) hydrolyzing the samples to provide hydrolyzed samples;(d) titrating the hydrolyzed samples with a basic reagent to determine avolume of the basic reagent necessary to neutralize a Lewis acid speciesof each sample; (e) calculating the acid content of each sample from thevolume of basic reagent determined in step (d); and (f) varying one ormore conditions of the reaction if the acid content is above or below atarget acid content to maintain the acid content at the target acidcontent.

Among other factors, it has been discovered that titration can be usedas a technique to successfully monitor the deactivation level of anionic liquid catalyst. The use of titration in the process fordetermining ionic liquid catalyst deactivation as disclosed hereinenables commercial exploitation of ionic liquid catalysts in alkylationand other chemical processes employing ionic liquid catalysts duringwhich ionic liquid catalysts become deactivated. Due to suchdeactivation, these chemical processes require monitoring ionic liquidcatalyst deactivation in order to maintain sufficient reaction. Ionicliquid catalysts are also expensive to replace. Thus, the use of ionicliquid catalysts in these chemical processes is economically feasibleonly when the catalysts can be efficiently regenerated and recycled. Theprocess for determining ionic liquid catalyst deactivation as disclosedherein and the other processes utilizing an embodiment of such processfor determining ionic liquid catalyst deactivation can maintainsufficient reaction during ionic liquid deactivating chemical processes.The present processes can also permit efficient regeneration of ionicliquid catalysts and recycling of such regenerated catalysts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting deactivation of a chloroaluminate ionicliquid catalyst, in terms of total acidity, as a function of time.

FIG. 2 is a graph depicting deactivation of a chloroaluminate ionicliquid catalyst, in terms of density, as a function of time.

FIG. 3 is a graph depicting deactivation of a chloroaluminate ionicliquid catalyst, in terms of aluminum content, as a function of time.

DETAILED DESCRIPTION Process for Determining Ionic Liquid CatalystDeactivation

Disclosed herein is a process for determining ionic liquid catalystdeactivation. According to such process, at least one sample of an ionicliquid catalyst is collected. The at least one sample is then hydrolyzedto provide at least one hydrolyzed sample. Thereafter, the at least onehydrolyzed sample is titrated with a basic reagent to determine a volumeof the basic reagent necessary to neutralize a Lewis acid species of theionic liquid catalyst. Subsequently, the acid content of the at leastone sample is calculated from the volume of basic reagent determinedabove.

Titration is a technique known in the art used to determine an unknownconcentration of a known reactant. An acid-base titration, like the oneutilized in the present process, can determine an unknown concentrationof a particular acid by neutralizing the acid with a particular base.Such an acid-base titration involves adding base having a knownconcentration to a known volume of acid having an unknown concentration.When the base neutralizes the acid, as indicated for example by anindicator, addition of base stops and the volume of base required forthe neutralization reaction is known. The chemical equation for theneutralization reaction between the particular acid and particular baseis also known. Thus, the concentration of the acid can be calculatedfrom the number of moles of base X that combine with the number of molesof acid Y in the chemical equation, the concentration of base, thevolume of base, and the volume of acid:

Concentration of acid=(X*concentration of base*volume of base)/(Y*volumeof acid)

In the present process, the acid is the Lewis acid species present inthe ionic liquid catalyst and the base is the basic reagent. Whiletitration is a basic analytical technique, the inventors of the presentapplication have discovered titration of ionic liquid catalyst with abasic reagent is a particularly useful and effective process fordetermining ionic liquid catalyst deactivation.

The present process is based in part on the discovery that an ionicliquid catalyst deactivation mechanism is the formation of by-productsknown as conjunct polymers.

The conjunct polymers can deactivate ionic liquid catalysts by formingcomplexes with or simply interacting with the ionic liquid catalyst. Itis believed that complexes form because conjunct polymers, by virtue oftheir double bonds, form pi (π) complexes with or sigma (σ) bonds withthe Lewis acid species, such as metal halides, in the ionic liquidcatalyst. As an example, conjunct polymers can complex with AlCl₃, aLewis acid present in chloroaluminate ionic liquid catalysts such as1-butyl-pyridinium heptachloroaluminate. Conjunct polymers may complexAlCl₃ via their double bonds to make reversible pi-complexes. Thepi-complexes may convert to irreversible sigma-complexes. Conjunctpolymers with their cationic character may also complex chloroaluminatespecies resulting in more deactivating complexes.

The term “conjunct polymer” as used herein refers to a polymericcompound that might bond to a cationic species of an ionic liquidcatalyst by pi bonding or sigma bonding or other means, which results inthe polymeric compound binding to the catalyst, so that it is notremovable by simple hydrocarbon extraction.

The term conjunct polymer was first used by Pines and Ipatieff todistinguish these polymeric molecules from the usual polymers. Unliketypical polymers, conjunct polymers are polyunsaturated cyclic,polycyclic and acyclic molecules formed by concurrent acid-catalyzedreactions including, among others, polymerization, alkylation,cyclization, and hydride transfer reactions. Conjunct polymers consistof an unsaturated intricate network of molecules that may include one ora combination of 4-, 5-, 6- and 7-membered rings and some aromaticentities in their skeletons. Some examples of the likely polymericspecies were reported by Miron et al. (Journal of Chemical andEngineering Data, 1963) and Pines (Chem. Tech, 1982), which documentsare incorporated by reference in their entirety herein. These moleculescontain double and conjugated bonds in intricate structures containing acombination of cyclic and acyclic skeletons.

In practice, conjunct polymers are also called “red oils” due to theircolor and “acid-soluble oils” due to their high uptake in the catalystphase where saturated hydrocarbons and paraffinic products are usuallyimmiscible.

Conjunct polymers can reduce the activity of the catalyst by twomechanisms. Increasing amounts of conjunct polymers dilute the activecomponents of the ionic liquid catalyst. Additionally, the conjunctpolymers bind or otherwise interact with the Lewis acid species (e.g.AlCl₃) in the ionic liquid catalyst forming complexes and weakening theacid strength of the catalyst. The two mechanisms can eventually renderthe catalyst ineffective for influencing reactions, such as analkylation reaction between isoparaffins and olefins.

Accordingly, ionic liquid catalyst deactivation is a function of theconcentration of the Lewis acid species (e.g. AlCl₃), which are notbound to or otherwise interacting with conjunct polymers and, therefore,have not formed complexes with conjunct polymers. As the concentrationof conjunct polymers in the ionic liquid phase increases, theconcentration of free Lewis acid species decreases and catalyst activitydecreases. Thus, it has been discovered that measuring the concentrationof free Lewis acid species is a way of measuring ionic liquid catalystdeactivation.

As discussed above, in the present process, at least one sample of ionicliquid catalyst is hydrolyzed. Hydrolyzing the ionic liquid catalystprovides at least one hydrolyzed sample, which includes protons. Theresultant at least one hydrolyzed sample with its protons is thentitrated with a basic reagent. During the titration step, the basicreagent reacts with the protons of the at least one hydrolyzed sample.From the titration, a volume of the basic reagent necessary toneutralize a Lewis acid species of the ionic liquid catalyst isdetermined. From this volume of basic reagent, the acid content of theat least one sample is calculated. As a result, ionic liquid catalystdeactivation, which corresponds to the concentration of the free Lewisacid species can be determined.

As an example, the ionic liquid catalyst N-butylpyridiniumheptachloroaluminate contains the free Lewis acid species, AlCl₃. Inparticular, 1 mole of N-butylpyridinium heptachloroaluminate contains 2mole AlCl₃. Hydrolyzing 1 mole of N-butylpyridinium heptachloroaluminateprovides 6 moles of protons, [H]⁺. Titrating this hydrolyzedN-butylpyridinium heptachloroaluminate with a basic reagent provides thevolume of basic reagent necessary to neutralize the AlCl₃. Since eachmole of AlCl₃ requires 3 moles of [OH]⁻ for titration, and the volume ofbasic reagent necessary to neutralize the AlCl₃ is known, the acidcontent of the N-butylpyridinium heptachloroaluminate can be calculatedas in any acid-base titration.

The process for determining ionic liquid catalyst deactivation, asdescribed herein, is unexpectedly advantageous over other possibleprocesses for determining ionic liquid catalyst deactivation. Inparticular, the process for determining ionic liquid catalystdeactivation, as described herein, is unexpectedly advantageous overboth measuring catalyst density and analyzing a particular element ofthe catalyst to determine ionic liquid catalyst deactivation.

Ionic liquid catalyst deactivation can be determined indirectly bymeasuring catalyst density. As discussed above, deactivation occurs viadilution of the catalyst by conjunct polymers. The density of conjunctpolymers is less than the density of the ionic liquid catalyst, whenfree from conjunct polymers. As conjunct polymers accumulate in thecatalyst phase, catalyst density decreases. Thus, catalyst densitydecreases upon catalyst deactivation.

While an on-line instrument such as a coriolis meter or densitomer maycontinuously monitor catalyst density, using catalyst density todetermine ionic liquid catalyst deactivation can be problematic attimes. Operational changes in the process in which the ionic liquidcatalyst is used may alter the conjunct polymer. Such changes in theconjunct polymer render catalyst density an unreliable measurement.Accordingly, caution must be exercised in correlating catalyst densitywith ionic liquid catalyst deactivation.

Elemental analysis of a key element in the catalyst is another usefulmethod for determining ionic liquid catalyst deactivation. However,analyzing a particular element of the catalyst to determine ionic liquidcatalyst deactivation can also be problematic at times. For example,aluminum content of a chloroaluminate ionic liquid catalyst correspondsto catalyst deactivation. However, measuring aluminum content is timeconsuming. Measuring aluminum content accurately is also difficultbecause the ionic liquid catalyst is sensitive to the atmosphericmoisture.

The present process of determining ionic liquid catalyst deactivationdoes not suffer from the shortcomings associated with measuring catalystdensity and elemental analysis. Titration provides accurate measurementsof the concentration of the Lewis acid species, whether or not there areoperational changes in the process that the ionic liquid catalystcatalyzes. A very small sample size (e.g. less than 1 gram) of ionicliquid can be accurately titrated. Furthermore, titration can beconducted quickly (e.g. within an hour of sample collection). Moreover,with titration, simple procedural safeguards can be taken to protect theionic liquid catalyst from exposure to the atmosphere.

Conjunct polymers form during a variety of reactions in which ionicliquid catalysts are employed, for example, alkylation, polymerization,dimerization, oligomerization, acetylation, olefin metathesis, andcopolymerization. The alkylation may be paraffin alkylation or aromaticalkylation. Conjunct polymers also form during olefin isomerization,desulfurization, and catalytic cracking Additionally, conjunct polymersare by-products of many types of Friedel-Crafts reactions, which arereactions that fall within the broader category of electrophylicsubstitution, like alkylation and acylation. Accordingly, the presentprocess is useful for determining deactivation of an ionic liquidcatalyst that has been used to catalyze any of these above-mentionedreactions.

In one embodiment, the ionic liquid catalyst has been used to catalyze areaction selected from the group consisting of paraffin alkylation,aromatic alkylation, polymerization, dimerization, oligomerization,acetylation, olefin metathesis, copolymerization, olefin isomerization,desulfurization, catalytic cracking, acylation and combinations thereof.

In one embodiment, the ionic liquid catalyst has been used to catalyze aFriedel-Crafts reaction. In another embodiment, the Friedel-Craftsreaction is alkylation.

The process for determining ionic liquid catalyst deactivation, asdescribed herein, can further include a step in which the acid contentof the at least one sample is compared to a predetermined value. Withsuch a comparison step, the present process may be used to monitordeactivation of an ionic liquid catalyst in a chemical process (e.g.alkylation) over time or may be used to monitor the quality of ionicliquid catalyst made during a catalyst manufacturing process.

In one embodiment, the predetermined value can be a percentage of theacid content of a fresh ionic liquid catalyst. In another embodiment,the predetermined value can be about 80% of the acid content of a freshionic liquid catalyst. As used herein, the term “fresh ionic liquidcatalyst” refers to ionic liquid catalyst that has not been subject todeactivation. These embodiments are especially useful for monitoringdeactivation of an ionic liquid catalyst in a chemical process (e.g.alkylation) over time.

Accordingly, the ionic liquid catalyst utilized in the present processcan be a catalyst which has been used in a reaction that producesby-product conjunct polymers and is therefore at least partiallydeactivated. In this case, the titration process is used to determinethe level of deactivation of this at least partially deactivatedcatalyst. When the catalyst's deactivation level reaches a predeterminedlevel, the ionic liquid catalyst can be regenerated.

In one embodiment, the predetermined value can be the acid content offresh ionic liquid catalyst. In another embodiment, the predeterminedvalue can be a predetermined acid content. These embodiments areparticularly useful for monitoring the quality of ionic liquid catalystmade during a catalyst manufacturing process.

Accordingly, the ionic liquid catalyst utilized in the present processcan be a fresh ionic liquid catalyst. Such fresh ionic liquid catalystcan be newly synthesized. In this manner, the present process can beused for quality control purposes.

Importantly, the at least one sample of an ionic liquid catalystcollected may be a plurality of samples collected at regular intervalsfrom a reaction employing the ionic liquid catalyst. In this manner, thepresent process is useful for monitoring ionic liquid catalystdeactivation. For example, the plurality of samples collected at regularintervals may originate from ionic liquid catalyst used in a chemicalreaction producing by-product conjunct polymers (e.g. alkylation). Assuch, the present process can be used to monitor ionic liquid catalystdeactivation during a chemical reaction catalyzed by the ionic liquidcatalyst. As another example, the plurality of samples collected atregular intervals may originate from ionic liquid catalyst produced in acatalyst manufacturing process. As such, the present process can be usedto monitor the quality of ionic liquid catalyst produced in a catalystmanufacturing process.

In the present process, the sample(s) of the ionic liquid catalystcollected may be less than 1 gram. The sample(s) titrated may also beless than 1 gram.

The basic reagent may be a hydroxide of a Group IA metal or a Group IIAmetal, including potassium hydroxide (KOH), sodium hydroxide (NaOH),rubidium hydroxide (RbOH), cesium hydroxide (CsOH), and barium hydroxide(BaOH₂). In one embodiment, the basic reagent is selected from the groupconsisting of potassium hydroxide, sodium hydroxide, rubidium hydroxide,cesium hydroxide, and barium hydroxide. In another embodiment, the basicreagent is potassium hydroxide.

Alkylation Process

The process for determining ionic liquid catalyst deactivation can beused in an alkylation process. In one embodiment, the alkylation processfirst involves reacting isoparaffins with olefins in the presence of anionic liquid catalyst to provide a hydrocarbon product. As used herein,the term “isoparaffin” means any branched-chain saturated hydrocarboncompound, i.e., a branched-chain alkane with a chemical formula ofC_(n)H_(2n+2). Examples of isoparaffins are isobutane and isopentane.The term “olefin,” as used herein, means any unsaturated hydrocarboncompound having at least one carbon-to-carbon double bond, i.e., analkene with a chemical formula of C_(μ)H_(2n). Examples of olefinsinclude ethylene, propylene, butene, and so on.

This embodiment further involves collecting samples of the ionic liquidcatalyst at regular intervals and hydrolyzing the samples to providehydrolyzed samples. The alkylation process then involves titrating thehydrolyzed samples with a basic reagent to determine a volume of thebasic reagent necessary to neutralize a Lewis acid species of eachsample. The acid content of each sample is then calculated from thevolume of basic reagent as determined above. Thereafter, the alkylationprocess includes regenerating the ionic liquid catalyst when the acidcontent reaches a predetermined level to provide a regenerated ionicliquid catalyst.

As used herein, the term “regenerated ionic liquid catalyst” refers toionic liquid catalyst that is either fully regenerated or partiallyregenerated. Fully regenerated ionic liquid catalyst is substantiallyfree from conjunct polymer-metal halide complexes. Partially regeneratedionic liquid catalyst still includes conjunct polymer-metal halidecomplexes such that it is not substantially free from conjunctpolymer-metal halide complexes. In the present alkylation process, theregenerated ionic liquid catalyst is typically fully regenerated.

Various methods of regenerating an ionic liquid catalyst are known inthe art. Such methods are described in detail in U.S. Patent ApplicationPublication Nos. 2007/0142218, 2007/0142217, 2007/0142215, 2007/0142214,2007/0142213, 2007/142211, 2007/0142216, 2007/0249486, and 2007/024985and a provisional U.S. patent application entitled “ElectrochemicalRemoval of Conjunct Polymers from Chloroaluminate Ionic Liquids,” whichis being filed concurrently with the present application. Thesedocuments are incorporated by reference in their entirety herein.

Process for Controlling Ionic Liquid Catalyst Activity in a ReactionProducing by-Product Conjunct Polymers

As discussed above, a variety of chemical reactions produce by-productconjunct polymers when catalyzed by ionic liquid catalysts. By-productconjunct polymers are not limited to ionic liquid catalyzed alkylationprocesses only. Reactions that produce by-product conjunct polymers whencatalyzed by ionic liquid catalysts include paraffin alkylation,aromatic alkylation, polymerization, dimerization, oligomerization,acetylation, olefin metathesis, copolymerization, olefin isomerization,desulfurization, catalytic cracking, and Friedel-Crafts reactions suchas alkylation and acylation. Any ionic liquid catalyzed reaction thatproduces by-product conjunct polymers is subject to ionic liquidcatalyst deactivation. Therefore, the above-described process fordetermining ionic liquid catalyst deactivation is useful for controllingionic liquid catalyst activity in such reactions.

In one embodiment, a process for controlling ionic liquid catalystactivity in a reaction producing by-product conjunct polymers involvesusing an ionic liquid catalyst in a reaction producing by-productconjunct polymers and collecting samples of the ionic liquid catalyst atregular intervals. Such process further involves hydrolyzing the samplesto provide hydrolyzed samples and titrating the hydrolyzed samples witha basic reagent to determine a volume of the basic reagent necessary toneutralize a Lewis acid species of each sample. Thereafter, such processinvolves calculating the acid content of each sample from the volume ofbasic reagent determined above and regenerating the ionic liquidcatalyst when the acid content reaches a predetermined level to providea regenerated ionic liquid catalyst.

Continuous Process for Maintaining Acid Content of an Ionic LiquidCatalyst at a Target Acid Content in a Reaction Producing by-ProductConjunct Polymers

The process for determining ionic liquid catalyst deactivation can alsobe used in a continuous ionic liquid catalyzed process that producesby-product conjunct polymers. During such a continuous ionic liquidcatalyzed process, it is desirable to maintain acid content of an ionicliquid catalyst at a target acid content. Such maintenance of ionicliquid catalyst acid content provides a steady-state reaction, includinga steady reaction rate and a steady reaction yield.

Accordingly, in one embodiment, a continuous process for maintainingacid content of an ionic liquid catalyst at a target acid content in areaction producing by-product conjunct polymers involves using an ionicliquid catalyst in a reaction producing by-product conjunct polymers andcollecting samples of the ionic liquid catalyst at regular intervals.Such process further involves hydrolyzing the samples to providehydrolyzed samples and titrating the hydrolyzed samples with a basicreagent to determine a volume of the basic reagent necessary toneutralize a Lewis acid species of each sample. Thereafter, such processinvolves calculating the acid content of each sample from the volume ofbasic reagent determined above and varying one or more conditions of thereaction if the acid content is above or below a target acid content.

The condition varying step of the continuous process maintains the acidcontent of the ionic liquid catalyst at the target acid content. Thetarget acid content may be a predetermined value or predetermined level.However, the target acid content may be a range of predetermined valuesor predetermined levels.

The condition varying step may also occur if the acid content is aparticular amount, for example, a particular percentage above or belowthe target acid content.

During the condition varying step, fresh ionic liquid catalyst may beadded to the reaction, the rate at which fresh ionic liquid catalyst isadded may be changed, used ionic liquid catalyst may be removed from thereaction, or the rate at which used ionic liquid catalyst is removedfrom the reaction may be changed. During the condition varying step,regenerated ionic liquid catalyst may be added to the reaction or therate at which ionic liquid catalyst is regenerated may be changed. Thus,the one or more conditions varied may be selected from the groupconsisting of adding fresh ionic liquid catalyst to the reaction, a rateof fresh ionic liquid catalyst added to the reaction, removing usedionic liquid catalyst from the reaction, a rate of removing used ionicliquid catalyst from the reaction, adding regenerated ionic liquidcatalyst to the reaction, a rate at which the ionic liquid catalyst isregenerated, and combinations thereof.

Ionic Liquid Catalyst

Any type of ionic liquid catalyst may be utilized in the processesdescribed herein. Ionic liquid catalysts are well known in the art.

As used herein, the term “ionic liquids” refers to liquids that arecomposed entirely of ions as a combination of cations and anions. Theterm “ionic liquids” includes low-temperature ionic liquids, which aregenerally organic salts with melting points under 100° C. and often evenlower than room temperature.

Ionic liquids may be suitable, for example, for use as a catalyst and asa solvent in alkylation and polymerization reactions as well as indimerization, oligomerization, acylation, olefin metathesis, andcopolymerization reactions.

One class of ionic liquids is fused salt compositions, which are moltenat low temperature and are useful as catalysts, solvents, andelectrolytes. Such compositions are mixtures of components, which areliquid at temperatures below the individual melting points of thecomponents.

The most common ionic liquids are those prepared from organic-basedcations and inorganic or organic anions. The most common organic cationsare ammonium cations, but phosphonium and sulphonium cations are alsofrequently used. Ionic liquids of pyridinium and imidazolium are perhapsthe most commonly used cations. Anions include, but are not limited to,BF₄ ⁻, PF₆ ⁻, haloaluminates such as Al₂Cl₇ ⁻ and Al₂Br₇ ⁻,[(CF₃SO₂)₂N]⁻, alkyl sulphates (RSO₃ ⁻), carboxylates (RCO₂ ⁻) and manyothers. The most catalytically interesting ionic liquids for acidcatalysis are those derived from ammonium halides and Lewis acids (suchas AlCl₃, TiCl₄, SnCl₄, FeCl₃, etc.). Chloroaluminate ionic liquids areperhaps the most commonly used ionic liquid catalyst systems foracid-catalyzed reactions.

Examples of such low temperature ionic liquids or molten fused salts arethe chloroaluminate salts. Alkyl imidazolium or pyridinium chlorides,for example, can be mixed with aluminum trichloride (AlCl₃) to form thefused chloroaluminate salts.

The processes as described herein can employ a catalyst compositioncomprising at least one aluminum halide such as aluminum chloride, atleast one quaternary ammonium halide and/or at least one aminehalohydrate, and at least one cuprous compound. Such a catalystcomposition and its preparation is disclosed in U.S. Pat. No. 5,750,455,which is incorporated by reference in its entirety herein.

Alternatively, the ionic liquid catalyst can be a chloroaluminate ionicliquid catalyst. For example, the chloroaluminate ionic liquid catalystcan be a pyridinium-based chloroaluminate ionic liquid catalyst, animidazolium-based chloroaluminate ionic liquid catalyst, and mixturesthereof. These ionic liquids have been found to be much more effectivein the alkylation of isopentane with ethylene than aliphatic ammoniumchloroaluminate ionic liquid (such as tributyl-methyl-ammoniumchloroaluminate).

The chloroaluminate ionic liquid catalyst can be: (1) a chloroaluminateionic liquid catalyst comprising a hydrocarbyl substituted pyridiniumhalide of the general formula A below and aluminum trichloride or (2) achloroaluminate ionic liquid catalyst comprising a hydrocarbylsubstituted imidazolium halide of the general formula B below andaluminum trichloride. Such a chloroaluminate ionic liquid catalyst canbe prepared by combining 1 molar equivalent hydrocarbyl substitutedpyridinium halide or hydrocarbyl substituted imidazolium halide with 2molar equivalents aluminum trichloride. The ionic liquid catalyst canalso be (1) a chloroaluminate ionic liquid catalyst comprising an alkylsubstituted pyridinium halide of the general formula A below andaluminum trichloride or (2) a chloroaluminate ionic liquid catalystcomprising an alkyl substituted imidazolium halide of the generalformula B below and aluminum trichloride. Such a chloroaluminate ionicliquid catalyst can be prepared by combining 1 molar equivalent alkylsubstituted pyridinium halide or alkyl substituted imidazolium halidewith 2 molar equivalents of aluminum trichloride.

wherein R═H, methyl, ethyl, propyl, butyl, pentyl or hexyl group and Xis a haloaluminate, and R₁ and R₂═H, methyl, ethyl, propyl, butyl,pentyl, or hexyl group and where R₁ and R₂ may or may not be the same.In one embodiment, the haloaluminate is a chloroaluminate. The ionicliquid catalyst can also be mixtures of these chloroaluminate ionicliquid catalysts.

Other examples of suitable chloroaluminate ionic liquid catalysts are1-butyl-4-methyl-pyridinium chloroaluminate (BMP), 1-butyl-pyridiniumchloroaluminate (BP), 1-butyl-3-methyl-imidazolium chloroaluminate(BMIM), 1-H-pyridinium chloroaluminate (HP), and N-butylpyridiniumchloroaluminate (C₅H₅C₄H₉Al₂Cl₇), and mixtures thereof.

A metal halide may be employed as a co-catalyst to modify the catalystactivity and selectivity. Commonly used halides for such purposesinclude NaCl, LiCl, KCl, BeCl₂, CaCl₂, BaCl₂, SiCl₂, MgCl₂, PbCl₂, CuCl,ZrCl₄, and AgCl as published by Roebuck and Evering (Ind. Eng. Chem.Prod. Res. Develop., Vol. 9, 77, 1970), which is incorporated byreference in its entirety herein. Especially useful metal halides areCuCl, AgCl, PbCl₂, LiCl, and ZrCl₄. Another useful metal halide isAlCl₃.

HCl or any Broensted acid may be employed as an effective co-catalyst toenhance the activity of the catalyst by boosting the overall acidity ofthe ionic liquid-based catalyst. The use of such co-catalysts and ionicliquid catalysts that are useful in practicing the present process aredisclosed in U.S. Published Patent Application Nos. 2003/0060359 and2004/0077914, the disclosures of which are herein incorporated byreference in their entirety. Other co-catalysts that may be used toenhance the catalytic activity of the ionic liquid catalyst include IVBmetal compounds. In one embodiment, the co-catalysts include IVB metalhalides such as TiCl₃, TiCl₄, TiBr₃, TiBr₄, ZrCl₄, ZrBr₄, HfC₄, andHfBr₄ as described by Hirschauer et al. in U.S. Pat. No. 6,028,024,which document is incorporated by reference in its entirety herein.

The following examples are provided to further illustrate the presentprocesses and advantages thereof. The examples are meant to be onlyillustrative, and not limiting.

EXAMPLES Example 1 Preparation of N-Butylpyridinium ChloroaluminateCatalyst

N-butylpyridinium chloroaluminate (C₅H₅C₄H₉Al₂Cl₇) ionic liquid catalystwas purchased. The catalyst had the following composition.

Wt % Al 12.4 Wt % Cl 56.5 Wt % C 24.6 Wt % H 3.2 Wt % N 3.3

Example 2 C₄ Olefin and Isobutane Alkylation

C₄ olefin alkylation with isobutane was performed in a 100 cccontinuously stirred tank reactor. A mixture of isobutane and 2-butenehaving a 8:1 molar ratio was fed to the reactor while vigorouslystirring at 1600 RPM. The chloroaluminate ionic liquid catalyst ofExample 1 was fed to the reactor via a second inlet port targeting tooccupy 8 vol % in the reactor. A small amount of anhydrous HCl gas wasadded to the process. The average residence time (combined volume offeeds and catalyst) was about 8 minutes. The outlet pressure wasmaintained at 100 psig using a backpressure regulator. The reactortemperature was maintained at 0° C. using external cooling. The reactoreffluent was separated in a 3-phase separator into C₄— gas, an alkylatehydrocarbon phase, and the ionic liquid catalyst. The ionic liquidcatalyst was recycled back to the reactor continuously. The amount ofcatalyst in the system was about 220 g, and the catalyst circulation was100 g/hour. After 19 hours of continuous operation, approximately 20 ccof the used catalyst was drained, and 20-30 g of fresh catalyst wasadded. The draining of used catalyst and addition of fresh catalyst wererepeated at 33, 36, 43, 57 and 75 hours. The run was stopped after 81hours on stream.

Example 3 Measurement of Properties of Fresh and Used Catalyst

The total acidity of the fresh catalyst used in Example 2 and the usedcatalyst drained in Example 2 was determined using an acid/basetitration method as follows. An automatic potentiometric titrator wasset up using 100 mL of nitrogen purged, de-aerated water and isopropylalcohol mixture in a beaker. The solution in the beaker was blanketedwith dry nitrogen gas and stirred. Using an airtight syringe, a catalystsample was drawn to transfer approximately 0.05 g into the beaker. Theweight charged to the beaker was determined by difference to the nearest0.0001 g. The catalyst sample charged to the beaker dissolved in thewater/isopropyl mixture rapidly, and the pH value of the solutiondecreased. The resulting solution was titrated with standardized 0.1 NKOH solution to the same potential as the blank. A well-definedinflection point was shown in the resulting titration curve around pH 7.From the amount of KOH solution consumed for the titration, the totalacidity was calculated as milligram equivalent of KOH (meq) required totitrate one gram of catalyst to a specified end point. Relative aciditywas calculated as percent retention of acidity from the fresh ionicliquid catalyst.

The density of the fresh catalyst used in Example 2 and the usedcatalyst drained in Example 2 was measured in a glove box using a 10 mlvolumetric flask and a four decimal point balance.

The aluminum content of the fresh catalyst used in Example 2 and theused catalyst drained in Example 2 was measured using an ICP method.Since the samples were moisture sensitive, the weighing was done in aglove box.

Table 1 provides the total acidity, relative acidity, density, andaluminum content of the fresh catalyst used in Example 2 and the usedcatalyst drained in Example 2.

TABLE 1 Total Acidity, Relative meq OH/g acidity, Density, catalyst %g/cc Wt % Al Fresh Catalyst 696 100 1.320 12.07 Used Catalyst Sample #1— — 1.303 10.83 Used Catalyst Sample #2 580 83.3 1.261 11.25 UsedCatalyst Sample #3 644 92.5 1.259 11.72 Used Catalyst Sample #4 650 93.41.290 11.49 Used Catalyst Sample #5 590 84.8 1.242 10.4 Used CatalystSample #6 572 82.1 1.210 9.64 Used Catalyst Sample #7 512 73.6 1.211 9.4

Example 4 Catalyst Deactivation Based on Total Acidity

FIG. 1 shows catalyst deactivation, based on total acidity and as afunction of hours on stream, as determined in Example 3. As the catalystwas deactivated upon extended operation, undesirable oligomericby-product yield in the alkylate gasoline increased. To maintainalkylation reaction selectivity, the total acidity of the catalystshould be maintained at >80% of the initial acidity.

Example 5 Catalyst Deactivation Based on Density

FIG. 2 shows catalyst deactivation, based on density and as a functionof hours on stream, as determined in Example 3. To maintain alkylationreaction selectivity, the density of the catalyst should be maintainedat >1.21 g/cc.

Example 6 Catalyst Deactivation Based on Aluminum Content

FIG. 3 shows catalyst deactivation, based on aluminum content and as afunction of hours on stream, as determined in Example 3. To maintainalkylation reaction selectivity, the aluminum content of the catalystshould be maintained at >9.5 wt % Al.

Although the present processes have been described in connection withspecific embodiments thereof, it will be appreciated by those skilled inthe art that additions, deletions, modifications, and substitutions notspecifically described may be made without departing from the spirit andscope of the processes as defined in the appended claims.

1. A process for controlling ionic liquid catalyst activity in areaction producing by-product conjunct polymers, comprising: (a) usingan ionic liquid catalyst in a reaction producing by-product conjunctpolymers; (b) collecting samples of the ionic liquid catalyst at regularintervals; (c) hydrolyzing the samples to provide hydrolyzed samples;(d) titrating the hydrolyzed samples with a basic reagent until thebasic reagent neutralizes a Lewis acid species of the ionic liquidcatalyst, as indicated by an indicator, to determine a volume of thebasic reagent necessary to neutralize the Lewis acid species of eachsample; (e) calculating an acid content of the hydrolyzed samples fromthe volume of basic reagent determined in step (d); and (f) regeneratingthe ionic liquid catalyst when the acid content reaches or falls below apredetermined lower level to provide a regenerated ionic liquidcatalyst.
 2. The process according to claim 1, wherein the reaction isselected from the group consisting of paraffin alkylation, aromaticalkylation, polymerization, dimerization, oligomerization, acetylation,olefin metathesis, copolymerization, olefin isomerization,desulfurization, catalytic cracking, acylation, and combinationsthereof.
 3. The process according to claim 1, wherein the predeterminedlower level is a percentage of an acid content of a fresh ionic liquidcatalyst that has not been subject to deactivation.
 4. The processaccording to claim 3, wherein the predetermined lower level is about 80%of the acid content of the fresh ionic liquid catalyst that has not beensubject to deactivation.
 5. The process according to claim 4, whereinthe acid content of the fresh ionic liquid catalyst that has not besubject to deactivation is greater than 650 meq OH/g.
 6. The processaccording to claim 1, wherein the predetermined lower level is 512 meqOH/g or greater.
 7. The process according to claim 6, wherein thepredetermined lower level is 572 meq OH/g or greater.
 8. The processaccording to claim 1, wherein the indicator is an inflection point in atitration curve.
 9. The process according to claim 1, wherein the ionicliquid catalyst is a chloroaluminate ionic liquid catalyst.
 10. Theprocess according to claim 1, wherein the ionic liquid catalyst is apyridinium-based chloroaluminate ionic liquid catalyst.
 11. The processaccording to claim 1, wherein the basic reagent is selected from thegroup consisting of potassium hydroxide, sodium hydroxide, rubidiumhydroxide, cesium hydroxide, and barium hydroxide.
 12. The processaccording to claim 1, wherein the samples collected in step (b) are lessthan 1 gram.
 13. The process according to claim 1, wherein amounts ofthe hydrolyzed samples that are titrated are less than 1 gram.
 14. Theprocess according to claim 1, wherein the titrating is done within anhour of the collecting.
 15. The process according to claim 1,additionally comprising maintaining an aluminum content in the samplesof ionic liquid catalyst at greater than 9.5 wt %.
 16. The processaccording to claim 1, additionally comprising maintaining a density inthe samples of ionic liquid catalyst at greater than 1.21 g/cc.
 17. Theprocess according to claim 1, wherein the titration is performed withsafeguards to protect the hydrolyzed samples from exposure to anatmosphere.
 18. The process according to claim 17, wherein thesafeguards comprise a blanket of dry nitrogen gas.
 19. The processaccording to claim 1, wherein the hydrolyzing and titrating areperformed in a same beaker.